The invention relates to a drive system for moving a lockable vehicle part and, more particularly, to a drive system having a drive element operating with a change in length, the element being supported at its ends on the vehicle part and on the body. The drive system also has a releasable snap lock by which the vehicle part is locked in one of its end positions. The snap lock is released by a control stroke of the driving element actively connected with the release mechanism of the snap lock. The control stroke precedes the working stroke to move the vehicle part by connecting one end of the driving element with a release mechanism.
A drive system of the above-mentioned type is known from U.S. Pat. No. 2,999,683 for moving a trunk lid between its open and closed positions. The upper end of the drive element is mounted on a bearing block on the trunk lid, while the lower end of the drive element is supported on a bearing block on the body by a rocker bearing forming the release mechanism. If the drive element is driven in the "extend" direction with the trunk lid closed, the lever arm of the rocker bearing articulated at the lower end of the drive element is initially pivoted downward, with the lock of the trunk lid being triggered by a cable connection to the lever arm. As the drive element extends further, the lever arm strikes a stop, whereupon the trunk lid is raised into its open position by the drive element.
One disadvantage of the known drive system is the fact that considerable space is required in the vehicle and is not available in every vehicle design.
There is therefore needed a drive system of the above-mentioned type in which the space required to install the drive system can be made smaller.
These needs are met by a drive system for moving a locking vehicle part. The drive system includes a drive element operating with a change in length, the element being supported at its ends on the vehicle part and on the body. The drive system also has a releasable snap lock by which the vehicle part is locked in one of its end positions. The snap lock is released by a control stroke of the driving element actively connected with the release mechanism of the snap lock. The control stroke precedes the working stroke to move the vehicle part by connecting one end of the driving element with a release mechanism. A rotary joint is provided as the, release mechanism for the control stroke of the driving element such as a hydraulic cylinder.
It is an advantage of the present invention that a pivot pin is slidably guided in an elongated hole to form the rotary joint. In particular preferred embodiments, the length of the elongated hole is set for the control stroke of the drive element and the pivot pin is automatically locked in its opposite end positions in the elongated hole. The pivot pin is locked via a leaf spring pair by whose arrangement the displacement path of the pivot pin is increasingly narrowed toward the center of the length of the elongated hole.
In still further preferred embodiments, the elongated hole is provided at one end area of the drive element. The elongated hole is made in a foot of the drive element and the pivot pin is mounted immovably on the body.
In still further preferred embodiments, a pivotable supporting frame of the motor vehicle lid is movable by a driving element such as a hydraulic cylinder. The motor vehicle lid is mounted to pivot in the opposite direction on the supporting frame.
In another preferred embodiment, the driving element that operates with a change in length is a double-acting hydraulic cylinder.